1. The Electron Configuration

2. C12-2-06 ELECTRON CONFIGURATION
OUTCOME QUESTION(S):
C ELECTRON CONFIGURATION
Relate the electron configuration of an element to its valence electron(s) and its position on the Periodic Table.
Include: quantum energy level, shapes, and orbitals.
Write the electron configuration for a variety of atoms and ions using the 3 configuration laws.
Include: shorthand notation and valence configuration
Vocabulary & Concepts 
Pauli Exclusion Principle Hund Rule
Aufbau Principle

3.  Electron Configuration
These are the two ways of representing electron location – we will focus on Electron Configuration more often 
Orbital Box Diagrams 1s 2s 2p 3s 3p 3d 4s

4.  Electron Configuration of Zn2+
1s2
2s2
2p6
3s2
3p6
3d10
 Electron Configuration of Zn2+
n = 2
2e-
8e-
18e-
n = 1
2e-
8e-
8e-
OLD way
NEW way

5. There are 3 main rules for “placing” electrons in configuration
NUCLEUS
There are 3 main rules for “placing” electrons in configuration 1s
Level
Shapes
orbitals
e- capacity 1 s
1 = 1 2
s,p
1+3 = 4 8 3
s,p,d
1+3+5 = 9 18 4
s,p,d,f
= 16 32 n
n types n2
2n2 2s 2p 3s 3p 3d 4s 4p 4d 4f

6. Use up (↑) and down arrows (↓) to indicate opposite spin
1. Pauli Exclusion Principle
Electrons are constantly spinning which creates a magnetic field
Only two electrons can occupy the same orbital and only if they have opposite spins
Use up (↑) and down arrows (↓) to indicate opposite spin

7. 2. Aufbau Principle
Unexcited electrons fill the lowest, most stable, energy orbital available – ground state.
This is no different from the “old” model – fill the lowest shell before moving to outer shells

8. The “get your own room” principle – no one wants a bunkmate
3. Hund rule
Electrons must enter empty orbitals of equal energy first before joining occupied orbitals.
The “get your own room” principle – no one wants a bunkmate

9. Periodic Table actually displays the Aufbau principle for electron configuration of elements.
Task: find the element needed, consider the total number of electrons, and use the configuration pattern of the table

10. Carbon has all the electrons of previous elements plus 1 more
Draw orbital box / electron configuration for C:
move along the table writing the configuration C 1s 2s 2p
C: 1s2 2s2 2p2
Carbon has all the electrons of previous elements plus 1 more

11. Notice we passed the configuration of Carbon…
Draw orbital box / electron configuration for Mg:
move along the table writing the configuration Mg
Notice we passed the configuration of Carbon… 1s 2s 2p 3s
Mg: 1s2 2s2 2p6 3s2

12. “Germanium has all the electrons of Argon plus these more”
Draw electron config for germanium:
Ge – atomic number 32
Ge: s2 3d10 4p2
1s2 2s2 2p6 3s2 3p6
[Ar]
Orbits fill in increasing energy: notice the “d” levels fill out of order…
Shorthand notation uses noble gas “kernels.”
Ge: [Ar] 4s2 3d10 4p2
“Germanium has all the electrons of Argon plus these more”

13. Find the last filled Noble Gas to use as the kernel
Write the shorthand configurations for Mn and Ag. 1 2 3 4 5
Find the last filled Noble Gas to use as the kernel
Mn: [Ar] 4s2 3d5
Ag: [Kr] 5s2 4d9

14. Valence configuration - 2s2 2p5
Valence configuration includes the electrons in the outer-most or highest quantum level (n).
F = 9 electrons
1s2 2s2 2p5
Valence configuration - 2s2 2p5
It’s not just the last ones, but the total electrons in the outer quantum level
Ge = 32 electrons
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p2
Valence configuration - 4s2 4p2

15. Valence electrons are removed from the highest quantum level
F-1 = 9 electrons + 1 gained
1s2 2s2 2p5
The ION configuration is 1s2 2s2 2p6
Valence electrons are removed from the highest quantum level
Fe+2 = 26 electrons – 2 lost
1s2 2s2 2p6 3s2 3p6 4s2 3d6
The ION configuration is 1s2 2s2 2p6 3s2 3p6 3d6

16. Some exceptions to the rule:

17. Half-filled and completely filled orbitals have extra stability
Electron Promotion
Half-filled and completely filled orbitals have extra stability
Atoms will “promote” similar electrons to improve overall stability
Look for configurations ending in “p2” ,“p5” OR “d4” ,“d9” - one electron away from being half or complete filled…”

18. *Promotion accounts for multiple ionization states (Fe+2, Fe+3…)
Cr: [Ar] 4s2 3d4 Cu: [Ar] 4s2 3d9 4s 3d 4s 3d
Actual configurations:
Cr: [Ar] 4s1 3d5 Cu: [Ar] 4s1 3d10
*Promotion accounts for multiple ionization states (Fe+2, Fe+3…)
Think of this as moving a CFO into a CEO at a company – you don’t move the mailperson…

19. C12-2-06 ELECTRON CONFIGURATION
CAN YOU / HAVE YOU?
C ELECTRON CONFIGURATION
Relate the electron configuration of an element to its valence electron(s) and its position on the Periodic Table.
Include: quantum energy level, shapes, and orbitals.
Write the electron configuration for a variety of atoms and ions using the 3 configuration laws.
Include: shorthand notation and valence configuration
Vocabulary & Concepts 
Pauli Exclusion Principle Hund Rule
Aufbau Principle